Okay look, this has been an issue for TOO LONG. Voice chat for Linux users seems to be broken. Either it doesn't work at all, or if it does work, steam crashes randomly when using it. It probably hasn't been fixed because no one has directly reported this to Valve, so my suggestion is... well... we report it valve. I'm not sure how you would go about doing that, if someone does know please post. This issue can probably be fixed easily, Valve just needs to know about it first. So please, make a fuss about this, spam Valve in anyway possible about this issue, it really, REALLY needs to be fixed.

They already know about it for about 1.5 months.See this entry on their issue tracker: TF2 crashes when using microphone[github.com]But please DON'T COMMENT unless you contribute in a way that will help fix this problem, remember this is an *issue tracker* and not a discussion forum. So please no "+1" or "this needs to be fixed" or "bump" since this won't help anyone and just makes everything harder.

Another user confirmed that avoiding using pulseaudio avoided the crash, so the problem may be in pulseaudio. Anybody who confirms they avoid crashing by disabling pulseaudio should report that to the pulseaudio guys so that they can collect information.